| 摘要 |
PURPOSE:To form a large notch on the way of a metallic hollow pipe which is apt to cause core deflection, by notching at a single stroke plural small notches divided at equal internals, moving it by a constant stroke in the lengthwise direction, and notching the remaining part in the same way. CONSTITUTION:A remaining projecting piece 2 of equal interval length D is placed so as to divide the opening length L of a large notch 1, and plural small notches are notches at a single stroke. Subsequently, it is moved by a constant stroke S in the lengthwise direction, a remaining part containing plural remaining projecting pieces 2 is notched at a single stroke in the same way as above, and a large notch 1 is formed. At first, a mandrel C is inserted into the hollow inside of a material M, is set to a band groove 7 of a lower mold A, and a fixed pin 18 of through-holes 10, 17 of the lower mold A and the mandrel C is made to pass through and is fixed. Subsequently, plural small notches 3 are notched by lowering a moving upper mold B. Subseqently, only the material M is moved by a constant stroke in the lengthwise direction, the upper mold B is lowered in the same way as above, and the large notch 1 having the opening length L is notched and formed. |
